Masonry · Lintels, openings & bearing
Masonry wall with an opening: piers, lintel, bearing calculator
Unreinforced masonry wall with a window or door opening carrying a line load from the floor or roof. Load to each pier (its own width plus half the opening, including the masonry self-weight), simplified compression capacity φ·k·f′m·Ab with the slenderness reduction k, lintel load with or without arching, and the concentrated bearing under the lintel ends.
Standard: AS 3700-2018 Cl 7.3 simplified compression (k, Srs), Cl 7.3.5 concentrated loads · arching over openings
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Wall length | 6 | m |
| Wall height | 2.7 | m |
| Leaf thickness | 190 | mm |
| Unit strength f′uc | 15 | MPa |
| Mortar factor km (M3 hollow = 1.6, solid = 1.4) | 1.6 | |
| Top support | Concrete slab over (k = 0.67 − 0.02(Srs − 14)) | |
| Opening width | 1.8 | m |
| Opening start from the left end | 1.6 | m |
| Opening height | 1.2 | m |
| Sill height | 0.9 | m |
| Design line load on top (1.2G + 1.5Q) | 30 | kN/m |
| Masonry unit weight | 15 | kN/m³ |
| Lintel bearing length | 150 | mm |
| Concentrated-load factor kb | 1 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| f′m = km√f′uc | 6.20 | MPa |
| Srs = H/t | 14.2 | |
| Slenderness reduction k | 0.666 | |
| Masonry over the opening | 0.60 m → no arching, full load | |
| Lintel load / M* | 57.7 kN / 13.0 kNm | |
| Left pier (1.60 m): N* / φFo | 92 / 941 | kN |
| Right pier (2.60 m): N* / φFo | 131 / 1,529 | kN |
| Lintel end reaction / bearing capacity | 28.8 / 132.5 | kN |
- ✓ Left pier — 10 %
- ✓ Right pier — 9 %
- ✓ Bearing under the lintel ends
- ✓ Piers at least 2t wide
- ✓ k > 0 (wall not too slender)
Method, formulas and assumptions
- Simplified method (Cl 7.3.3): Fo = φ·k·f′m·Ab, φ = 0.75; k = 0.67 − 0.02(Srs − 14) under a concrete slab, 0.67 − 0.025(Srs − 10) otherwise, Srs = avH/ktt with av = kt = 1 (supported top and bottom).
- Each pier carries the line load over its own width plus half the opening, with the masonry self-weight (× 1.2).
- Arching: when the masonry above the opening is taller than the 60° triangle (plus 150 mm), the lintel only carries the triangle of masonry; otherwise it carries the full load.
- Concentrated bearing: φ·kb·f′m·Ab with kb = 1 (conservative); a spreader or bond beam raises it to the Cl 7.3.5 value.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.